In NLP (Natural Language Processing), a "language pair" means two languages that are being used together to translate text. For example, if we want to change text from English to Spanish, the language pair would be English-Spanish. The first language (English) is the one we start with, and the second language (Spanish) is the one we want to end up with. You could also have a language pair created from Spanish to English, where Spanish is the language we start with, and English is the language we end up with.
Language pairs are important for Avodah's Natural Language Processing (NLP) team because that information helps computers understand how to change words and sentences from one language to another. Different language pairs can be easier or harder to work with depending on how similar or different the languages are.